7.To do this, he must be at least as knowledgeable as the dealer.

to do this : in order to discover a rarity

8.Like a scientist bent on making a discovery, he must cherish the hope that one dayhe will be amply rewarded.

bent on / upon : 决心于,adj.短语作定语修饰scientist

Ex

He is bent on winning the game.

He is bent on becoming a bridge player.

近义表达

be bent on doing sth / be determined on doing sth / be devoted to / be engaged in新概念英语1

9.He has often described to me how he picked up a masterpiece for a mere $50.

for :花费

A mere : only

10.He found a great deal to interest him.

He found a lot of interesting things.

这2个句型要求背诵

11.The morning passed rapidly and Frank was about to leave when he noticed a large packing case lying on the floor.

be about to do sth:将要，正打算

be about to ...when ( /at the moment ).......:表示正要或刚要干什么，突然

Ex

I was about to leave when the telephone rang.

He was about to lock door when his friend visited him.